Dynamic Characterization of Monumental Building for SHM Purpose: The Case of the Papal Basilica of St Peter

Health assessment of ancient buildings is a challenging task, especially with big and complex structures, undergoing continuous changes through the ages. Within a wider project aimed at getting a deep structural knowledge of the most iconic monument of Christianity, the Papal Basilica of Saint Peter in Vatican City, it has also been decided to devote some effort in defining the dynamic behavior of the main body and the façade, which date back to the 17th century, in view of a possible continuous dynamic monitoring. The best possible set-up has been devoted to the measurements, then used in a cross validation of a numerical Finite Element Model of the Basilica. These tests are an essential preliminary step for the analysis of the structural global dynamic response, providing precious information to both optimize the experimental setup and the sensor positions, in view of the design of a permanent Structural Health Monitoring (SHM) system. With the aim to fully simulate the static and dynamic response, a Finite Element (FE) model was developed, based on a 3D CAD model and coordinated with the Digital Twin, which was updated according to the results coming from previous investigations. The comparison between experimental measurements and numerical simulations, despite the complexity of both the measurements and the model, revealed a more than satisfactory correspondence and a clear building dynamic behavior, confirming the reliability of the Updated FE Model to allow defining the Basilica behavior and also offering a tool to describe and simulate eventual critical scenarios, thanks to a distributed and continuous SHM system.